"The youngest billionaires are Mohammed Dewji of Tanzania and Igho Sanomi, a Nigerian oil trader. They are both 38 years old," the report adds.

A survey indicates there are far more African billionaires than previously thought but the number of Africans living in extreme poverty has also shot up.

HIDE FORTUNE DETAILS

Previous Africa-rich-lists named as few as 16 billionaires, but Ventures said its exhaustive research had identified at least 55 on a continent where the wealthy often fiercely protect details about their fortunes.

The pan-African business magazine said it was able to uncover dozens of new billionaires by using "on-the-ground knowledge" to overcome hurdles that may have "hampered" other researchers.

The most prominent South African named is Nicky Oppenheimer, worth an estimated $6.5 billion, whose fortune came largely from the diamond mines his family controlled for decades, which were operated by De Beers. Oppenheimer sold his family's stake in De Beers two years ago.

CORRUPTION RIFE

The figure of 55 is "actually an under-estimate" of Africa's billionaires, Chi-Chi Okonjo, the founder of Ventures, told AFP.

"People are not comfortable disclosing their wealth," he said.

Corruption is rife on the continent and the rule of law still unevenly applied.

African business moguls often face accusations that their fortunes were illegitimately earned, including with extra-legal help from political patrons.

The apparently rising number of ultra-rich Africans has come amid broader economic growth on the continent, which has seen an average of five per cent GDP expansion since 2010.

But economic growth has not kept up with a rising population.

"There are more than twice as many extremely poor people living in sub-Saharan Africa today (414 million) than there were three decades ago (205 million)," the World Bank said in April.

It is the only region where "the number of poor people individuals has risen steadily and dramatically," over the last 30 years, the bank said.